Our company recently bought a PicoScope 2204A. I successfully wrote Software to use it. But last week I found out that I can't connect to the scope if any cables (other than USB or probes) are connected to it.

1. With a 50 Ohm BNC cable connected only to the PicoScope, the PicoScope 6 Software freezes at “Listing devices” and can only by terminated via the task manager.

2. With a 50 Ohm BNC cable connected to the PicoScope and to a Waveform Generator putting out a signal, the PicoScope 6 Software displays a “no oscilloscope found” error message.

3. With a 50 Ohm BNC cable connected to the PicoScope and to a Waveform Generator NOT putting out a signal, the PicoScope 6 Software works correctly.

4. If no cable is connected to the PicoScope, the PicoScope 6 Software works correctly.

5. If I connect the supplied probe I do not have any of the problems stated above.

The same behaviour applies to my own software (written in LabWin C).
We would like to use the PicoScope in testing equipment so the case No. 1 could easly happen if the tester forgets to plug in the cables. Even for developing it's really annoying to unplug every cable before running the software.

Is there a setting that I miss where I have to specify the impedance of the input channels?

Or did I screw over some setting in the 2204A? I always call the ps2000_close_unit() function when I close my software. However it could have happened that I shut down the unit in a non-conforming way during debugging.

All trace files above 0.45V input voltage show a HW Error. I also noticed that two relays in the Picoscop act differently depending on the input voltage. At >0.45V they switch in rapid succession. Below 0.45V they switch with a significant pause, one after the other. This sounded a lot like a power issue we sometimes have with other PCBs.
This made me suspicious and I wanted to verify my setup before I post here again. And I indeed found the problem. The power connector to the USB Isolation Adapter was not making contact (Since there are no power LEDs on that thing, it was not apparent). Everything works fine now.

So I assume that if the input signal rises above the 0.4V the internal relays have to switch in a different order. Because the provided power to the PicoScope was not high enough the scope threw the HW-Error.

Thanks a lot for the quick reply and the fix for problem No 1.
I still posted the entire procedure and attached the trace files. Maybe it's helpful to someone.

tl;dr
2204A Scope would not connect if on startup a signal was at the input.
On startup the relays sounded differently depending on input voltage.
InLine USB Isolator did not supply enough power (was not connected).

We have a connection problem with our "old" 3425 (Serial XFY08/023). The new SW "PicoScope® 6 - PC-Oszilloskop-Software Version: 6.10.16.2" cannot connect to the device. It is not able to recognize the device.